Medical injector with ratcheting plunger

ABSTRACT

A medical injector has a body with a displaceable plunger. The plunger includes a plurality of spaced-apart ratchet teeth disposed along the length thereof. At least one indexer is provided to engage the plunger, wherein the indexer is configured to allow the plunger to displace distally toward a distal end of the body but not proximally toward a proximal end of the body. The medical injector also includes an actuator having an engagement portion formed to engage one or more of the ratchet teeth. The actuator is displaceable to a ready state, the engagement portion being displaced proximally relative to the plunger with the actuator being displaced to the ready state. The indexer prevents proximal movement of the plunger, thereby allowing the engagement portion to bypass one or more of the ratchet teeth with the actuator being displaced to the ready state. In addition, the actuator is displaceable from the ready state to cause actuation of the medical injector. The displacement from the ready state causes distal displacement of the engagement portion with the engagement portion engaging one or more of the ratchet teeth and causing distal displacement of the plunger with the engagement portion.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of U.S. patent application Ser. No.13/064,315 filed Mar. 17, 2011, which is a continuation-in-part ofInternational Patent Application No. PCT/US2009/057429, filed in Englishon Sep. 18, 2009 and designating the United States. International PatentApplication No. PCT/US2009/057429 claims priority under 35 USC §119(e)from U.S. Provisional Patent Application Ser. No. 61/192,468, filed onSep. 18, 2008. The entirety of all of said prior applications is herebyincorporated by reference.

FIELD OF THE INVENTION

This invention relates to displaceable medical injector plungers and,more particularly, to ratcheting medical injector plungers.

BACKGROUND OF THE INVENTION

Medical injectors are well known in the art, including syringes and peninjectors. Medical injectors typically include a plunger for advancingone or more stoppers in delivering a medicament during an injection.Although it is known in the prior art to provide syringe plungers withteeth or other features to prevent retraction and re-use after aninitial injection, syringe plungers are typically actuated throughdirect application of linear force. Dose size is a direct function ofplunger displacement. It may be difficult to control linear displacementof the plunger, thus resulting in difficulty over control of dose size.

As for pen injectors, a lead screw or rotating plunger is provided whichis mechanically coupled to a dose-setting knob or other actuator througha series of mechanical connections. The typical pen injector mechanismis fairly complex and consists of multiple cooperating parts. For costsreasons and simplicity of use, a minimum number of working parts isdesired.

SUMMARY OF EMBODIMENTS OF THE INVENTION

Accordingly, it is an aspect of the present invention to provide aplunger for a medical injector which may be controllably advanced with aminimum number of cooperating parts.

The foregoing and/or other aspects of the present invention are achievedby providing a medical injector including a body having a distal end anda proximal end, and a displaceable plunger disposed in the body. Theplunger includes a plurality of spaced-apart ratchet teeth disposedalong the length thereof. At least one indexer is provided and is formedto engage the plunger, wherein the indexer is configured to allow theplunger to displace distally toward a distal end of the body but notproximally toward a proximal end of the body. The medical injector alsoincludes an actuator having an engagement portion formed to engage oneor more of the ratchet teeth. The actuator is displaceable to a readystate, the engagement portion being displaced proximally relative to theplunger with the actuator being displaced to the ready state. Theindexer prevents proximal movement of the plunger thereby allowing theengagement portion to bypass one or more of the ratchet teeth with theactuator being displaced to the ready state. In addition, the actuatoris displaceable from the ready state to cause actuation of the medicalinjector. The displacement from the ready state causes distaldisplacement of the engagement portion with the engagement portionengaging one or more of the ratchet teeth and causing distaldisplacement of the plunger with the engagement portion.

The foregoing and/or other aspects of the present invention are alsoachieved by providing a medical injector including a body having adistal end and a proximal end, and a plunger displaceably disposed inthe body. The plunger includes a plurality of spaced-apart ratchet teethdisposed along the length thereof. The plunger selectively displaces astopper to dispense a medicament from said medical injector. The medicalinjector also includes an indexer disposed within the body to engage theplunger to permit distal displacement of the plunger and substantiallyprevent proximal displacement of the plunger, and an actuator having anengagement portion to engage the plunger to permit proximal displacementof the actuator relative to the plunger and substantially prevent distaldisplacement of the actuator relative to the plunger. Upon proximaldisplacement of the actuator relative to the body to a ready state, oneor more of the ratchet teeth bypass the engagement portion to proximallydisplace the actuator relative to the plunger. Upon distal displacementof the actuator relative to the body from the ready state, the actuatorengages one or more of the ratchet teeth to distally displace theplunger relative to the indexer to distally displace the stopper todispense medicament from the medical injector.

The foregoing and/or other aspects of the present invention are alsoachieved by providing a medical injector including a body having adistal end and a proximal end, and a plunger displaceably disposed inthe body. The plunger includes a plurality of spaced-apart ratchet teethdisposed along the length thereof. The plunger selectively displaces astopper to dispense a medicament from said medical injector. The medicalinjector also includes an indexer disposed within the body to engage theplunger to permit distal displacement of the plunger and substantiallyprevent proximal displacement of the plunger. The medical injectoradditionally includes actuating means for actuating the medical device,the actuating means having engagement means for engaging the plunger topermit proximal displacement of the actuating means relative to theplunger and substantially prevent distal displacement of the actuatingmeans relative to the plunger. Upon proximal displacement of theactuating means relative to the body to a ready state, one or more ofthe ratchet teeth bypass the engagement means to proximally displace theactuating means relative to the plunger. Upon distal displacement of theactuating means relative to the body from the ready state, the actuatingmeans engages one or more of the ratchet teeth to distally displace theplunger relative to the indexer to distally displace the stopper todispense medicament from the medical injector.

The foregoing and/or other aspects of the present invention are alsoachieved by providing a method of injecting a medicament from a medicalinjector having a body with distal and proximate ends. The methodincludes the operations of permitting distal displacement of a plungerwith respect to the body and substantially preventing proximaldisplacement of the plunger with respect to the body, and permittingproximal displacement of an actuator relative to the plunger andsubstantially preventing distal displacement of the actuator relative tothe plunger. The method also includes the operations of proximallydisplacing the actuator relative to the body to a ready state, therebyproximally displacing the actuator relative to the plunger, and distallydisplacing the actuator relative to the body from the ready state,thereby engaging the plunger and distally displacing the plungerrelative to the body to dispense medicament from the medical injector.

Additional and/or other aspects and advantages of the present inventionwill be set forth in part in the description that follows and, in part,will be apparent from the description, or may be learned by practice ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects and advantages of embodiments of theinvention will become apparent and more readily appreciated from thefollowing detailed description, taken in conjunction with theaccompanying drawings, in which

FIG. 1 is a perspective view of a medical injector in accordance with anembodiment of present the invention;

FIG. 2 is partial perspective view of a plunger usable with the injectorof FIG. 1;

FIG. 3 is a partial cross-sectional view taken along line 3-3 of FIG. 2;

FIGS. 4-6 are perspective partial cross-sectional views illustratingoperation of the medical injector of FIG. 1;

FIGS. 7 and 8 are perspective views respectively illustrating tworockers usable with the injector of FIG. 1;

FIGS. 9-11 are perspective partial cross-sectional views illustratingoperation of a medical injector in accordance with an embodiment of thepresent invention using the rocker of FIG. 7;

FIGS. 12 and 13 are perspective partial cross-sectional viewsillustrating the use of a multi-link rocker in accordance with anembodiment of the present invention;

FIG. 14 shows a dose counter usable with an embodiment of the presentinvention;

FIG. 15 is a partial perspective view of a pivotable actuator usablewith the plunger of FIG. 2;

FIGS. 16 and 17 are perspective partial cross-sectional viewsillustrating use of the pivotable actuator of FIG. 15;

FIG. 18 is a cross-sectional view of a medical injector in accordancewith another embodiment of the present invention;

FIG. 19 is a perspective view of an embodiment of a second portion of anactuator of the medical injector of FIG. 18;

FIG. 20 is a partial cross-sectional view of the medical injector ofFIG. 18;

FIGS. 21 and 22 illustrate alternative embodiments of grooves of thesecond portion of FIG. 19;

FIG. 23 is a perspective view of another embodiment of a second portionof the actuator of the medical injector of FIG. 18;

FIG. 24 is a perspective view of a body of the medical injector of FIG.18;

FIG. 25 is a perspective view of yet another embodiment of the secondportion of the actuator of the medical injector of FIG. 18;

FIG. 26 is a partial perspective view of the medical injector of FIG. 18with the second portion of FIG. 25;

FIG. 27 illustrates another embodiment of a groove of the second portionof FIG. 19;

FIG. 28 is a perspective view of the medical injector in accordance withanother embodiment of the present invention;

FIG. 29 is a perspective view of an embodiment of an actuator and arocker of the medical injector of FIG. 28;

FIGS. 30 and 31 are perspective views of a body of the medical injectorof FIG. 28;

FIGS. 32 and 33 are perspective views of a rotary knob of the medicalinjector of FIG. 28;

FIG. 34 is a partial cross-sectional view of a limiter rib forpreventing dose setting beyond an available amount;

FIG. 35 is a cross-sectional view of a medical injector in accordancewith another embodiment of the present invention;

FIG. 36 is a perspective cross-sectional view of the medical injector ofFIG. 35 taken along line 36-36 of FIG. 35;

FIG. 37 is a perspective view of a medical injector according to anotherembodiment of the present invention;

FIG. 38 is a perspective view of a plunger usable with the medicalinjector of FIG. 37;

FIG. 39 is a cross-sectional view of the medical injector of FIG. 37taken along line 39-39 of FIG. 37;

FIG. 40 is a cross-sectional view illustrating the operation of themedical injector of FIG. 37; and

FIG. 41 is a perspective view of another embodiment of a plunger usablewith the medical injector of FIG. 37.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Reference will now be made in detail to embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. The embodiments described herein exemplify, but do notlimit, the present invention by referring to the drawings. As will beunderstood by one skilled in the art, terms such as up, down, bottom,and top are relative, and are employed to aid illustration, but are notlimiting.

With reference to the figures, a medical injector 10 is shown having aratchetable plunger 12 provided therewith. As will be appreciated bythose skilled in the art, the medical injector 10 may be of variousforms, including being a syringe or pen injector. In accordance with anembodiment of the present invention, the medical injector 10 isparticularly well-suited for administering at least one fixed dose, andis even better suited for administering a series of fixed doses. Themedical injector 10 may be configured in any way known to be compatiblewith the plunger 12 as described herein. The medical injector 10 mayinclude a reservoir 14 for accommodating an injectable medicament, whichmay be a drug cartridge, or which may be formed directly in the medicalinjector 10. The reservoir 14 may have one or more stoppers 16associated therewith as known in the art. The medical injector 10 mayalso be provided with a needle 18 for injection which may be removablyattached or affixed to the medical injector 10 such as in a “staked”arrangement.

The plunger 12 is elongated and generally flat. A plurality ofspaced-apart ratchet teeth 20 are disposed along the length of theplunger 12. In a preferred arrangement, the plunger 12 includes aplate-shaped body 22 having opposing first and second faces 24, 26. Theratchet teeth 20 are disposed on the first face 24 and, in a furtherpreferred arrangement, also on the second face 26. Preferably, theratchet teeth 20 on the first and second faces 24, 26 are axiallyaligned along the length of the plunger 12.

The ratchet teeth 20 are configured to permit unidirectional movement ofthe plunger 12. Particularly, with reference to FIG. 3, the ratchetteeth 20 are preferably saw-tooth shaped having a ramped surface 28 anda shoulder stop 30. As shown in FIG. 3, the ramped surfaces 28 of theratchet teeth 20 on both the first and second surfaces 24, 26 areoriented to face in the same general direction. The shoulder stops 30extend transversely from the first and second faces 24, 26, preferablyat a substantially perpendicular orientation.

The plunger 12 may also have one or more rails 27 extending from thefirst face 24 and/or the second face 26. The rails 27 may be formed toslide through one or more corresponding shape-mating slots formed in themedical injector 10. The rails 27 may provide stability during use,particularly during translation of the plunger 12.

With reference to FIGS. 4-6, the plunger 12 is disposed in a body 32 ofthe medical injector 10. The body 32 includes a distal end 34, locatedto be directed toward a patient during an injection, and a proximal end36, located to be away from a patient during an injection (FIG. 1).During use, the medical injector 10 is configured to permit the plunger12 to move unidirectionally therein in a distal direction toward thedistal end 34, but not in a proximal direction toward the proximal end36. To facilitate such unidirectional movement, at least one indexer 38is provided formed to engage the plunger 12. The indexer 38 isconfigured to allow the plunger 12 to displace distally toward thedistal end 34 of the body 32 but not proximally toward the proximal end36 of the body 32.

The indexer 38 includes a deflectable pawl 40 which, as shownschematically in FIG. 3, includes a ramped engagement surface 42 and anoutward facing stop surface 44. The indexer 38 is outwardly deflectableto permit the engagement surface 42 to ascend the ramped surface 28 ofan individual of the ratchet teeth 20 with the plunger 12 movingdistally relative thereto. With sufficient distal movement, the indexer38 bypasses the ratchet teeth 12, and under inherent resilience of theindexer 38, snaps inwardly such that the stop surface 44 is aligned withthe shoulder stop 30. Preferably, the stop surface 44 is formed to begenerally parallel to the shoulder stop 30. With rearward (proximal)movement of the plunger 12, the shoulder stop 30 and the stop surface 44interferingly engage thus preventing proximal movement of the plunger12. In a preferred embodiment, a pair of the indexers 38 are provided soas to act against the ratchet teeth 20 located on both the first andsecond faces 24, 26, as shown in FIGS. 4-6. It is further preferred thata pair of the indexers 38 be provided which are axially aligned thusproviding a pinching effect to the plunger 12. This pinching effect mayprovide a stable holding force for the plunger 12.

The indexer 38 may be formed to be deflectable through inherentresilience, such as through material selection (e.g., being formed of athermoplastic). In addition, or alternatively, the indexer 38 mayinclude a cantilevered arm 46 which permits deflection of the associatedpawl 40. The indexer 38 is formed to have a natural, unbiased state asshown in FIGS. 4-6, where the indexer 38 is positioned to act againstthe shoulder stop 30 of the ratchet teeth 20. The cantilevered arm 46 isformed with sufficient internal memory to provide the unbiased state forthe indexer 38.

The medical injector 10 also includes an actuator 48 having anengagement portion 50 formed to engage one or more of the ratchet teeth20. The engagement portion 50 preferably includes an engagement pawl 52having a ramped engagement surface 54 and an outward facing stop surface56 configured like the pawl 40 described above. Preferably, two of theengagement portions 50 are provided located to engage the ratchet teeth20 located on the first and second faces 24, 26.

With reference to FIG. 4, the plunger 12 is positioned to engage one ofthe stoppers 16. To cause actuation of the medical injector 10, as shownin FIG. 5, the actuator 48 is moved to a ready state, with theengagement portion 50 moving proximally. The indexer 38 preventsproximal movement of the plunger 12, thus allowing the actuator 48 tomove proximally relative to the plunger 12. With the plunger 12 beingheld stationary, and the engagement portion 50 moving proximallyrelative to the plunger 12, the engagement portion 50 bypasses one ormore of the ratchet teeth 20. The actuator 48 is displaced sufficientlyto achieve a ready state.

For actuation of the medical injector 10, the actuator 48 is displacedfrom the ready state with distal movement of the engagement portion 50.The engagement portion 50 engages one or more of the ratchet teeth 20,particularly with interfering engagement between the shoulder stop 30and the stop surface 56. In particular, the engagement portion 50engages the next distal ratchet tooth 20. Distal movement of theengagement portion 50 causes the plunger 12 to move distally therewith.Distal movement of the plunger 12, in turn, causes distal advancement ofthe stopper 16 in causing an injection to be administered. The ratchetteeth 20 are able to bypass the indexer 38 in the distal direction.

The size of a dose to be administered by the medical injector 10 is afunction of the spacing between the ratchet teeth 20 and/or the amountof proximal displacement of the engagement portion 50 relative to theratchet teeth 20 with the actuator 48 moving to a ready state. To createa fixed dose, one or more keys 58 may be defined on the medical injector10 and/or the actuator 48 which are formed to nest within and slidealong corresponding channels 60 formed in the medical injector 10 and/orthe actuator 48. As shown in FIGS. 4-6, it is preferred that the keys 58be formed on the actuator 48 and the channels 60 be formed in themedical injector 10. With reference to FIG. 4, the keys 58 are at thedistal end of the channel 60, prior to use. With proximal displacementof the actuator 48, the keys 58 are proximally advanced in the channels60 to a proximal-most position corresponding to the ready state of theactuator 48. The length of the travel of the keys 58 in the channels 60restricts the range of movement of the actuator 48 in defining the sizeof the dose administrable by the medical injector 10. As shown in FIGS.5 and 6, the keys 58 are advanced distally with the actuator 48 duringuse to a distal-most position.

The actuator 48 shown in FIGS. 4-6 is a linear slide actuator whichapplies force directly to the plunger 12. As will be appreciated bythose skilled in the art, the actuator 48 may be of variousconfigurations. With reference to FIGS. 7-8, the actuator 48 may includea rocker 62 pivotally mounted thereto. The rocker 62 is frame-shaped,having a first end 64 for pivotal mounting to the actuator 48 and asecond opposing end 66 for pivotally mounting to the medical injector10. The engagement portion 50 is located between the first and secondends 64, 66. As shown in FIGS. 7 and 8, two of the engagement portions50 may be provided to coact with the ratchet teeth 20 being located onthe first and second faces 24, 26.

It is noted that the spacing between the first and second ends 64, 66affects force transmission from the actuator 48 to the plunger 12particularly in the generation of torque. The spacing L between thefirst and second ends 64, 66, as well as the spacing S1, S2 of theengagement portion 50 from the first and second ends 64, 66, affects howtorque is generated and transmitted to the plunger 12.

With reference to FIG. 9, the actuator 48 is shown in an initial pre-usestate with the rocker 62 being inclined distally. With reference to FIG.10, the actuator 48 has been advanced to the ready state with the rocker62 having been drawn proximally with rotation about the second end 66 soas to be inclined in a proximal direction. During this movement, theengagement portion 50 bypasses one or more of the ratchet teeth 20 inthe same manner as described above. As shown in FIG. 11, the actuator 48is displaced from the ready state to cause actuation of the medicalinjector 10. With displacement of the actuator 48 from the ready state,the rocker 62 is caused to advance distally about the second end 66 withthe engagement portion 50 causing the plunger 12 to also advancedistally. Dose size may be restricted both by the key 58/channel 60arrangement described above and/or by the range of motion of the rocker62.

As will be appreciated by those skilled in the art, the rocker 62 may bedirectly coupled to the actuator 48, as shown in FIGS. 9-11. As will beappreciated by those skilled in the art, a multi-link arrangement may beused to couple the rocker 62 to the actuator 48. With reference to FIGS.12 and 13, one or more links 68 may be connected between the rocker 62and the actuator 48 to provide force for displacement thereof. Anyarrangement of the links 68 may be utilized which transmits force fromthe actuator 48 to the rocker 62. As shown in FIGS. 12 and 13, two ofthe links 68 (68A, 68B) are utilized with the link 68A being pivotallyconnected to the actuator 48 and pivotally connected to the link 68B,and with the link 68B being pivotally connected to the link 68A andpivotally connected to the rocker 62. The links 68A, 68B collectivelytransmit force to the rocker 62.

With reference to FIGS. 15-17, the actuator 48 may be arranged to benon-linearly displaced. As shown in FIGS. 15-17, the actuator 48 may beformed to pivot about a fulcrum 70. With the actuator 48 pivotingoutwardly from the medical injector 10 about the fulcrum 70, theengagement portion 50 is caused to be displaced proximally. Conversely,inward pivoting of the actuator 48 about the fulcrum 70 causes distaldisplacement of the engagement portion 50. The engagement portion 50coacts with the plunger 12 in the same manner as described above.

With reference to FIGS. 15 and 16, the medical injector 10 is shown in apre-use state. To facilitate handling of the actuator 48, a grip ring orpad 72 may be provided which extends radially outwardly from the medicalinjector 10 to facilitate displacement of the actuator 48. To preparefor use, as shown by the arrow in FIG. 16, the actuator 48 is pivoted toa ready state as shown in FIG. 17. To cause actuation of the medicalinjector 10, the actuator 48 is pivoted inwardly from the ready state,as shown by the arrow in FIG. 17.

The size of the dose may be fixed with the actuator 48 being pivotableby limiting the range of rotation of the actuator 48. A portion 74 ofthe medical injector 10 may be configured to limit the range of rotationof the actuator 48, particularly outward rotation, such limited rangecorresponding to the ready state.

The actuator 48 may be formed as a linear slide actuator, but configuredto accept a non-linear force to adjust the actuator 48 to the readystate. With reference to FIGS. 18-27, the actuator 48 may include afirst portion 48A, formed in accordance with the description above. Inaddition, the actuator 48 may include a rotatable second portion 48Bcoupled to the first portion 48A so as to be rotatable relative thereto.This arrangement permits rotational adjustment of the actuator 48 to theready state. Rotational adjustment is typical of pen-type injectors andmay be preferred by some users.

The second portion 48B is accessible exteriorly of the medical injector10 so as to be engageable from the outside by a user; particularly, thesecond portion 48B extends proximally from the proximal end 36 of thebody 32. The first and second portions 48A, 48B are rotatably coupled inany known manner. By way of non-limiting example, the second portion 48Bmay be formed with a continuous ring 80 seated in channel 82 of thefirst portion 48A. The ring 80 is sized and shaped to rotate freelywithin the channel 82 with the first and second portions 48A, 48B beingaxially fixed to move together. As will be appreciated by those skilledin the art, the ring 80 and the channel 82 may be reversed on the firstand second portions 48A, 48B.

As shown in FIG. 19, a groove 84 is formed about an exterior of thesecond portion 48B. One or more keys 86 are located on surroundingportions of the medical injector 10, e.g., on the body 32, about thesecond portion 48B positioned and sized to be seated in the groove 84 soas to be moveable along the length thereof. The length of the groove 84delimits the extent of rotation of the second portion 48B. According toone embodiment, the groove 84 is at least partially helical so as tohave a screw thread shape. As will be appreciated by those skilled inthe art, the key(s) 86 may be located on the exterior of the secondportion 48B and the corresponding groove 84 may be formed on surroundingportions of the medical injector 10.

Rotation of the second portion 48B in a first rotational directionresults in proximal displacement of the first and second portions 48A,48B with corresponding proximal displacement of the engagement portion50 to the ready state. In particular, rotation of the second portion 48Bresults in proximal displacement thereof and, in concert, proximaldisplacement of the first portion 48A and of the engagement portion 50.The first portion 48A is non-rotatably displaced proximally. The lengthof the groove 84 limits the extent of rotation of the second portion 48Bthereby limiting the dose that may be administered. Once rotated to aset dose, the dose may be administered by pressing the second portion48B, which results in distal advancement of the second portion 48B and,correspondingly, distal non-rotating advancement of the first portion 48along with the engagement portion 50.

With distal advancement of the second portion 48B, it is preferred thatthe second portion 48B be advanced linearly without rotation. To thisend, it is preferred that the groove 84 be formed with a first helicalportion 84 a and a second axial portion 84 b extending from the firsthelical portion 84 a generally parallel to the longitudinal axis of thesecond portion 48B. Referring to FIG. 21, with this arrangement, the oneor more keys 86 traverse the first helical portion 84 a with rotation ofthe second portion 48B in a proximal direction. Elbow 88 is defined atthe junction of the first helical portion 84 a and the second axialportion 84 b which limits the extent of rotation and, thus, proximaldisplacement of the second portion 48B. The elbow 88 defines the readyposition of the actuator 48. For actuation, the second portion 48B isdepressed and caused to advance distally linearly without rotation withthe one or more keys 86 traversing the second axial portion 84 b. This,in turn, causes distal advancement of the first portion 48A and distaladvancement of the plunger 12 through engagement with the engagementportion 50. The linear displacement of the second portion 48B permitsforce applied thereto to be fully transmitted in one axial direction,without resolution into two or more components. As such, the full forceof actuation applied to the second portion 48B is transmitted to theactuator 48.

For a single-dose version of this arrangement, a single set of the firsthelical portion and the second axial portion 84 a, 84 b may be utilized.For multiple dosing, as shown in FIG. 22, the groove 84 may be extendedsuch that a secondary helical portion 84 a′ may extend directly from theterminus of the second axial portion 84 b which extends into a secondaryaxial portion 84 b′ and so forth as needed. According to one embodiment,a series of the first helical portions 84 a and second axial portions 84b may be defined continuously about the second portion 48B to facilitatemultiple dosing. According to one embodiment more than one groove 84 maybe utilized with a corresponding set of one or more keys 86. Also, oneor more of the grooves 84 and one or more of the keys 86 may be locatedon the second portion 48B and/or surrounding portions of the medicalinjector 10.

Preferably, reverse rotation of the second portion 48B should beavoided. To this end, as shown in FIGS. 23-24, one or more detents 90may be formed on the second portion 48B formed to snap engage one ormore locating channels 92 formed on the medical injector 10 about thesecond portion 48B, such as on the body 32. Preferably, a locatingchannel 92 is located corresponding to the second portion 48B being inthe ready position, and such a ready position locating channel 92 iselongated such that the detent 90 may be displaced along the lengththereof with the second portion 48B during dose administration. As willbe appreciated by the skilled in the art, the detent(s) 90 may be formedon the medical injector 10 and the locating channels may be formed onthe second portion 48B.

In addition, reverse axial movement along the second axial portion 84 b,particularly after injection, is undesired. To this end, as shown inFIGS. 25 and 26, a locking tab 94 is provided on the second portion 48Bwhich is configured to snap engage into a locking channel 96 at aposition coinciding with an end of the injection (e.g., positioncoinciding with the one or more keys 86 reaching the terminus of thesecond axial portion 84 b at the end of a dosing stroke). Axial movementof the second portion 48B is thus limited. The locking channel 96 may beconfigured to permit rotation of the locking tab 94 for separationtherefrom with rotation of the second portion 48B in preparing for asubsequent dose. The locking channel 96 is formed on a surroundingportion of the medical injector 10, such as on the body 32. As will beappreciated by those skilled in the art, the locking tab 94 may beformed on the medical injector 10 and the locking channel 96 may beprovided on the second portion 48B.

Further, as will be appreciated by those skilled in the art, with thearrangement discussed above, particularly with the use of the first andsecond portions 84 a, 84 b of the groove 84, doses are fixed doses.According to one embodiment to allow for variable dosing, the secondportion 48B may be allowed to rotate during distal advancement of thesecond portion 48B with the one or more keys 86 traveling along thegroove 84. Thus, in this embodiment, as shown in FIG. 27, only thehelical portion 84 a of the groove 84 need be provided. With thisarrangement, the second portion 48B may be rotated to any location alongthe groove 84 (84 a) to set a dose with reverse rotation along thegroove 84 (84 a) permitting dosing. A scale, or other index, as known inthe art may be provided to correspond to rotational displacement of thesecond portion 48B to provide indication of the set dose amount. Tolimit unwanted reverse rotation, and to retain position at a set dose, areleasable retention arrangement, as is in known in the art, may beutilized.

The first and second portions 48A, 48B may be utilized with any of thefeatures described herein. Preferably, the first and second portions48A, 48B are used in conjunction with the rocker 62.

FIG. 28 is a perspective view of the medical injector 10 in accordancewith another embodiment of the present invention. With reference toFIGS. 28-33, medical injector 10 includes a body 32, a rotary knob 100rotatably connected to the body 32, an actuator 48 disposed within thebody 32, and a cap 101 connected to the actuator 48. As shown in FIG.29, the actuator 48 includes the groove 84 as described above. Theactuator 48 also includes an axial groove 102. The axial groove 102interacts with an axial key 104 (shown in FIG. 30) disposed on aninterior of the body 32 to guide axial movement of the actuator 48 withrespect to the body 32 and prevent rotation of the actuator 48 withrespect to the body 32. As will be appreciated by those skilled in theart, the axial groove 102 may be disposed on the interior of the body 32and the axial key 104 may be disposed on the actuator 48, withoutdeparting from the scope of the invention.

As shown in FIG. 31, the body 32 also includes a circumferential groove106 disposed at a proximal end thereof for connection with the rotaryknob 100, as will be described in greater detail below. Additionally, aswill be described in greater detail below, the body 32 includes acantilevered, circumferential arm 120 with a triangular protrusion 122disposed at an end thereof and protruding radially outward.

FIG. 32 is a perspective view of the distal end of the rotary knob 100and FIG. 33 is a perspective view of the proximal end of the rotary knob100. As shown in FIG. 32, the rotary knob 100 includes acircumferentially extending and radially inward protruding connector108. According to one embodiment, the connector 108 is substantiallywedge-shaped. To assemble the medical injector 10, the rotary knob 100is distally inserted over the proximal end of the body 32 until theconnector 108 slips into the circumferential groove 106 of the body 32,connecting the rotary knob 100 to the body 32. The wedge shape of theconnector 108 secures the rotary knob 100 to the body 32, substantiallypreventing proximal displacement of the rotary knob 100 relative to thebody 32 while permitting rotation of the rotary knob 100 relative to thebody 32.

As shown in FIG. 32, the connector 108 is disposed in a large diameterportion 110 of the rotary knob 100. Also disposed in the large diameterportion 110 of the rotary knob 100 is a triangular groove 112. Thetriangular groove 112 interacts with the triangular protrusion 122 onthe arm 120 to permit unidirectional rotation of the rotary knob 100with respect to the body 32. That is, the triangular groove 112 and thetriangular protrusion 122 interact to permit rotation of the rotary knob100 only in a direction to advance the plunger 12 proximally. The rotaryknob 100 also has a reduced diameter portion 114 which prevents proximaldisplacement of the rotary knob relative to the body subsequent toconnection between the connector 108 and the circumferential groove 106.Additionally, a camming projection or key 116 projects radially inwardfrom the reduced diameter portion 114. Similar to the key 86 describedabove, the key 116 interacts with the groove 84 of the actuator 48 toconvert rotational movement of the rotary knob 100 into proximal axialmovement of the actuator 48. Subsequent to the proximal axial movementof the actuator 48, the user depresses the cap 101 (connected to theactuator 48) to distally displace the actuator 48 relative to the body32, and thus distally advance the plunger 12.

Referring to FIG. 33, the rotary knob 100 also includes radially outwardprojecting ribs 118 at a proximal end thereof. The ribs 118 function asa user interface for the user to grasp and rotate the rotary knob 100.

As will be appreciated by those skilled in the art, the medical injector10 may be utilized with various features. With reference to FIGS. 12-14,a dose counter may be provided with the medical injector 10 which givesan indication of the number of available doses to be administered. Forexample, a series of dose indicating holes 76 may be formed in themedical injector 10, particularly to be visible from the outsidethereof. A pointer 78 may be provided on the actuator 48 and formed tobe visible through a single one of the dose indicating holes 76 in agiven instance. During use, with the plunger 12 being distally advanceddose by dose, the pointer 78 is likewise advanced along the series ofthe dose indicating holes 76. According to one embodiment, the number ofthe dose indicating holes 76 located distally of the pointer 78 providesas an indication of the remaining number of doses. With the pointer 78appearing in the distal-most of the dose indicating holes 76, indicationis provided that no remaining doses are available for administration.

It is preferred that the pointer 78 be formed of a contrasting colorrelative to the portion of the medical injector 10 located about thedose indicating holes 76, so that the pointer 78 is readily visiblethrough the dose indicating holes 76.

In addition, according to one embodiment shown in FIG. 34, a protrudinglimiter rib 98 may extend from a distal portion of the plunger 12located to coincide with the dosage setting on the plunger 12corresponding to the last amount of available drug in the reservoir 14.Accordingly, with a predetermined extent of distal advancement of theplunger 12, the limiter rib 98 is formed to interferingly engage aportion of the actuator 48 and block proximal movement therepast. Inthis manner, a dose greater than the available amount in the reservoir14 cannot be set by the actuator 48.

In the above-described embodiments, the plunger 12 is substantiallyflat. In contrast, in the following embodiments, the plungers aresubstantially cylindrical. For example, in the medical injector 140shown in FIGS. 35 and 36, the plunger 142 is substantially cylindricaland the ratchet teeth extend circumferentially around the plunger 142.In such an embodiment, the orientation of the plunger is not critical,thereby easing assembly of the device. In addition, as shown in FIGS. 35and 36, a pointer or indicator flag 144 connected to the plunger 142 isvisible to a user through indicating holes 146 to indicate the dosage.The pointer 144 engages an axial slot 148 in the actuator 150 to providean alignment feature.

FIG. 37 illustrates a medical injector 152 according to anotherembodiment of the present invention, FIG. 38 is a perspective view of aplunger usable with the medical injector 152, and FIG. 39 is across-sectional view of the medical injector 152. As shown in FIGS. 37and 39, the medical injector 152 includes a body 154 having axial slots156 therein, an actuator 158, a plunger slider or ring slider 160 witharms extending through the slots 156, and a mode selector 162. Accordingto one embodiment, the ratchet teeth on the plunger arecircumferentially discontinuous. Put another way, at least one portionof the plunger is axially free of ratchet teeth. FIG. 38 illustratesanother embodiment of a cylindrical plunger 164 in which the plunger 164is frusto-cylindrical. In other words, the plunger 164 has a pair offlat sides 166. As with the plunger 12, the plunger 164 also has aplurality of spaced-apart ratchet teeth 168 disposed along the lengththereof. The plunger 164 also has a pair of ring slider connectors 170disposed on the flat sides 166 and a mode selector connector 172disposed at a proximal end of the plunger 164. The illustrated modeselector connector 172 is substantially square. One skilled in the artwill appreciate that other shapes may be used without departing from thescope of the present invention. For example, the mode selector connector172 may be triangular, rectangular, pentagonal, or hexagonal, or mayhave more sides.

The mode selector 162 has a recess corresponding to the mode selectorconnector 172 to engage the mode selector connector 172. While in theillustrated embodiment, the male protrusion (mode selector connector172) is disposed at the proximal end of the plunger 166 and thecorresponding female recess is disposed on the distal end of the modeselector 162, one skilled in the art will appreciate that the maleprotrusion may be disposed on the distal end of the mode selector 162and the corresponding female recess may be disposed on the proximal andof the plunger 166 without departing from the scope of the presentinvention. The mode selector 162 is rotatably disposed with respect tothe actuator 158, and thereby, as described in greater detail below,provides an interface for a user to rotate the plunger 166.

Similar to the embodiments described previously, in one orientation, theratchet teeth 168 of the plunger 166 engage the pawls 174 of the indexer176 and the engagement pawls 178 of the actuator 158. But because of thedesign of the plunger 164 (including the flat sides 166), the plunger164 is rotatable with respect to the body 154. Accordingly, using themode selector 162, a user can rotate the plunger 164 to an orientationin which the ratchet teeth 168 are disengaged from the pawls 174 and theengagement pawls 178, and the flat sides 166 are aligned with the pawls174 and the engagement pawls 178, as shown in FIG. 39. Such an alignmentpermits selective, free distal and proximal displacement of the plunger164. This feature is useful, for example, for reconstituting alyophilized medicament, which will be discussed in greater detail below.

According to one embodiment, the ring slider connectors 170 disposed onthe flat sides 166 of the plunger 164 selectively engage the arms 180 ofthe ring slider 160 that extend inwardly through the slots 156 of thebody 154. For example, when a user rotates the mode selector 162 todisengage the ratchet teeth 168 from the pawls 174 and the engagementpawls 178, the ring slider connectors 170 rotate into engagement withthe arms 180 of the ring slider 160. The user then can use the ringslider 162 to control displacement of the plunger 164.

As shown in FIG. 39, medical injector 152 also includes a pointer 182for indicating the dosage, similar to the pointer 144. According toanother embodiment, in which the axial slots 156 are circumferentiallyenlarged to accommodate rotation of the ring slider 160, the plunger 164is fixedly connected to the ring slider 160, which serves as a dosageindicator.

Reconstitution of a lyophilized medicament will now be described withreference to FIG. 40. The stopper 184 is disposed on the distal end ofthe plunger 164 inside a cartridge 186 containing a diluent 188 therein.The medicament container 190 with a lyophilized medicament 192 disposedtherein is connected to a distal end of the cartridge 186 with adouble-ended needle 194 communicating between interior of the medicamentcontainer 190 and the cartridge 186. After the user rotates the modeselector 162 to disengage the ratchet teeth 168 from the pawls 174 andthe engagement pawls 178, the user distally slides the ring slider 160,thereby distally displacing the plunger 164 and the stopper 184, andexpelling the diluent 188 into the medicament container 190. Subsequentto the reconstitution of the lyophilized medicament 192, the userproximally slides the ring slider 160, thereby proximally displacing theplunger 164 and the stopper 184, and drawing the reconstitutedmedicament into the cartridge 186. Thereafter, the user disconnects themedicament container 190 and rotates the mode selector 162 to reengagethe ratchet teeth 168 with the pawls 174 and the engagement pawls 178.At this point, the reconstituted medicament can be injected as describedabove.

In the medical injector employing a ratchet plunger similar to thosedescribed above, discrete dosage settings are determined by the pitch of(or spacing between) the ratchets. FIG. 41 is a perspective view of theplunger 194 in accordance with another embodiment of the presentinvention in which a user may select one of a plurality of predeterminedratchet spacings. As shown in FIG. 41, the plunger 194 has two sideswith and 196 and 198 with respective pluralities of spaced-apart ratchetteeth 200 and 202 disposed along the length thereof. The distancebetween ratchet teeth 200 is shown as D₁ and the distance betweenratchet teeth 202 is shown as D₂, which is greater than D₁. The plunger194 is rotatable with respect to the body 154 and the actuator 158 sothat a user can select a desired spacing between ratchet teeth to engagethe pawls 174 and the engagement pawls 178. According to one embodiment,the mode selector 162 and the actuator 158 have demarcationscorresponding to the various spacings of the ratchet teeth.

According to one embodiment, the plunger 194 also has a flat side 204 sothat the user can rotate the plunger 194 to an orientation in which theratchet teeth 168 are disengaged from the pawls 174 and the engagementpawls 178, and the flat side 204 is aligned with the pawls 174 and theengagement pawls 178. Thus, the plunger 194 can also be employed toreconstitute a lyophilized medicament.

In addition, although the plunger 194 is illustrated as having two sideswith respective pluralities of spaced-apart ratchet teeth, one skilledin the art will appreciate that the plunger 194 may have 3, 4, 5, 6, 7,8, 9, 10, or more sides with respective pluralities ofdifferently-spaced-apart ratchet teeth to provide a greater selectionfor a user without departing from the scope of the present invention.Additionally, although the pawls 174 and the engagement pawls 178 areillustrated as being opposing pairs, a single pawl 174 and a singleengagement pawl 178 may be employed to accommodate a greater number ofsides with differently spaced ratchet teeth on the plunger 194 withoutdeparting from the scope of the present invention.

Although only a few embodiments of the present invention have been shownand described, the present invention is not limited to the describedembodiments. Instead, it will be appreciated by those skilled in the artthat changes may be made to these embodiments without departing from theprinciples and spirit of the invention, the scope of which is defined bythe claims and their equivalents.

What is claimed is:
 1. A medical injector, comprising: a body having adistal end and a proximal end; a displaceable plunger disposed in thebody, the plunger having a plurality of spaced-apart ratchet teethdisposed along the length thereof; at least one indexer formed to engagethe plunger, wherein the indexer is configured to allow the plunger todisplace distally toward the distal end of the body but not proximallytoward the proximal end of the body; an actuator having an engagementportion formed to engage one or more of the ratchet teeth, wherein theactuator is displaceable to a ready state, the engagement portion beingdisplaced proximally relative to the plunger upon the actuator beingdisplaced to the ready state, the indexer preventing proximal movementof the plunger thereby allowing the engagement portion to bypass one ormore of the ratchet teeth upon the actuator being displaced to the readystate, and wherein the actuator is displaceable from the ready state tocause actuation of the medical injector, the displacement from the readystate causing distal displacement of the engagement portion with theengagement portion engaging one or more of the ratchet teeth and causingdistal displacement of the plunger; and a rotary knob rotatably disposedat a proximal end of the body; wherein one of the actuator and aninterior of the body comprises an axial groove and the remaining one ofthe actuator and the interior of the body comprises a correspondingaxial key slidably received in the axial groove to guide axialdisplacement of the actuator relative to the body and prevent rotationof the actuator relative to the body; wherein one of the actuator andthe rotary knob comprises a groove with a substantially helical portionand the remaining one of the actuator and the rotary knob comprises acorresponding key slidably received in the groove; and wherein rotationof the rotary knob induces displacement of the key relative to thegroove, thereby axially displacing the actuator relative to the body. 2.The medical injector according to claim 1, wherein the actuator isslidably displaceable relative to the body.
 3. The medical injectoraccording to claim 1, further comprising a rocker for determining forcetransmission from the actuator to the plunger and/or for defining adosage amount, the rocker being pivotably connected to the actuator andpivotably connected to the body.
 4. The medical injector according toclaim 1, wherein a plurality of dose indicating holes are formed in thebody, and wherein a pointer extends from the actuator, the pointer beingconfigured to be visible through a single one of the dose indicatingholes at an instance, the pointer providing an indication of theremaining number of doses in the medical injector.
 5. The medicalinjector according to claim 1, further comprising a limiter rib disposedon the plunger to correspond with a last amount of available medicament,wherein the limiter rib is configured to interferingly engage a portionof the actuator and block proximal movement of the actuator therepast.6. A medical injector, comprising: a body having a distal end and aproximal end; a plunger displaceably disposed in the body, the plungerhaving a plurality of spaced-apart ratchet teeth disposed along thelength thereof, the plunger selectively displacing a stopper to dispensea medicament from said medical injector; an indexer disposed within thebody to engage the plunger to permit distal displacement of the plungerand substantially prevent proximal displacement of the plunger; anactuator having an engagement portion to engage the plunger to permitproximal displacement of the actuator relative to the plunger andsubstantially prevent distal displacement of the actuator relative tothe plunger; and a rotary knob rotatably disposed at a proximal end ofthe body; wherein one of the actuator and an interior of the bodycomprises an axial groove and the remaining one of the actuator and theinterior of the body comprises a corresponding axial key slidablyreceived in the axial groove to guide axial displacement of the actuatorrelative to the body and prevent rotation of the actuator relative tothe body; wherein one of the actuator and the rotary knob comprises agroove with a substantially helical portion and the remaining one of theactuator and the rotary knob comprises a corresponding key slidablyreceived in the groove; wherein rotation of the rotary knob inducesdisplacement of the key relative to the groove, thereby axiallydisplacing the actuator relative to the body; wherein upon proximaldisplacement of the actuator relative to the body to a ready state, oneor more of the ratchet teeth bypass the engagement portion to proximallydisplace the actuator relative to the plunger; and wherein upon distaldisplacement of the actuator relative to the body from the ready state,the actuator engages one or more of the ratchet teeth to distallydisplace the plunger relative to the indexer to distally displace thestopper to dispense medicament from the medical injector.
 7. The medicalinjector according to claim 6, further comprising a rocker fordetermining force transmission from the actuator to the plunger and/orfor defining a dosage amount, the rocker being pivotably connected tothe actuator and pivotably connected to the body.
 8. The medicalinjector according to claim 6, wherein at least one key is formed toextend from one of the actuator and the body, and a channel is formed inthe remaining one of the actuator and the body, the key being configuredto be slidably received in the channel for defining a dosage amount. 9.The medical injector according to claim 6, further comprising a limiterrib disposed on the plunger to correspond with a last amount ofavailable medicament, wherein the limiter rib is configured tointerferingly engage a portion of the actuator and block proximalmovement of the actuator therepast.
 10. The medical injector accordingto claim 6, wherein a plurality of dose indicating holes are formed inthe body, and wherein a pointer extends from the actuator, the pointerbeing configured to be visible through a single one of the doseindicating holes at an instance, the pointer providing an indication ofthe remaining number of doses in the medical injector.